You might find it hard in a closed system to maintain the alkalinity needed for them to thrive long-term! Source: I study bivalves
Would a little agricultural runoff help?
Hard to say without knowing its composition. If rich in ammonium, the nitrification (oxidation to nitrate) might lead to lower alkalinity. If rich in nitrate, it might help alkalinity, but only if there's some lower oxygen area of the tank like a bank of sediment, where denitrification can happen
What do you recommend for a 1000L IBC tank?
5 oysters.
6, there be overage
You might find it hard in a closed system to maintain the alkalinity needed for them to thrive long-term! Source: I study bivalves
Would a little agricultural runoff help?
Hard to say without knowing its composition. If rich in ammonium, the nitrification (oxidation to nitrate) might lead to lower alkalinity. If rich in nitrate, it might help alkalinity, but only if there's some lower oxygen area of the tank like a bank of sediment, where denitrification can happen